Vertebroplasty has been developed to treat vertebral compression fractures, and consists of injecting medical bone cement under pressure through a cannula into a vertebral body. The bone is usually porous with bone marrow occupying the porous space. The cement injected into the vertebral body displaces the bone marrow and fills the bone cavity. The cement hardens in-situ providing mechanical strength and stability of the bone weakened by osteoporosis or other pathologies such as cancers.
Bone cements are usually formed by dispersing PMMA particles in a monomer. Once the particles and monomer are mixed together, the particles partially dissolve in the monomer and form an increasingly thick cohesive dough. This phase is often known as swelling. This phase is followed by a second phase: the polymerization of the cement, where the thick dough becomes a hard polymeric material. However, as the cement polymerizes, it becomes increasingly harder to inject. A number of procedures typically have to be aborted due to the high delivery pressure requirement, which results in insufficient or poor filling which may fail to augment the vertebral body adequately.
Another pertinent limitation related to cement leakage is the usual inability of physicians to stop the cement flow immediately when required. Due to the high injection pressure in the injection system and the viscous nature of the cement, important residual flow of the cement typically exists in the system even after the injection is stopped, and until the system is de-pressurized.
Accordingly, improvements are desirable.